ON-LINE event: http://www.theochem.uni-frankfurt.de/LesHouches2021 The event will focus on theoretical and experimental concepts as well as state-of-the-art methodologies in the study of photoinduced energy and charge transfer in molecular complexes, nanostructured materials, and biological aggregates. A focus area is the rapidly expanding investigation of these systems by nonlinear spectroscopies, necessitating intense exchange between experiment and theory.